1. Field of the Invention.
The subject invention relates to a rocker arm assembly with an improved, stronger bridge support for mounting the rocker arm assembly onto the cylinder head of an internal combustion engine.
2. Description of the Prior Art.
Rocker arms are well known components of internal combustion engines and have been in existence for as long as internal combustion engines have been in existence. U.S. Pat. No. 4,674,453 discloses a rocker arm assembly directed to the type of rocker arm assembly which is stud mounted onto the engine assembly. The rocker arm assembly utilizes no support means other than the aforementioned stud which thus renders the rocker more susceptible to failure than the rocker arm assembly to be described below. The present invention utilizes base and bridge support means which results in a mechanically stronger and more reliable rocker arm assembly.
The present invention enhances the structural integrity of rocker arm assemblies of the type used in high performance engines such as those used in racing. As is well known, engines used in racing are subjected to extreme operating conditions which result in excessive forces and stresses being applied to the mechanical parts of the engine, in particular, to those parts which oscillate continuously. Among the many components of the engine which experience the forces and stresses under extreme operating conditions are the rocker arms.
The function of the rocker arm assembly is to control the opening and closing of the engine valves at the correct instant of the cycle. Every cylinder must have at least one intake valve and one exhaust valve. The intake valve permits the fuel mixture to enter the cylinder and be contained therein until combustion occurs, and the exhaust valve allows the burned gases to escape. The primary purpose of the rocker arm is to translate the upward movement of the pushrod into a downward movement of the valve spring which opens the valve. The downward movement of the pushrod results in the decompression of the valve spring which closes the valve.
Rocker arms may be mounted on a shaft or on a pivot point for oscillation about that point. Shaft mounted rocker arms oscillate on a common shaft. The rocker arms are lubricated by oil passages that route oil through the block, cylinder head, shaft and rocker arm. Some rocker arms are mounted on studs.
Rocker arms, which are used to transmit movement from the pushrods into an oscillating motion about a pivot point, which alternately results in the opening and closing of the engine intake and exhaust valves, are especially vulnerable to mechanical failure as a result of the stresses and forces which are imposed on them during high operating conditions. As mentioned in U.S. Pat. No. 4,674,453, when an engine is operating at peak RPM's, the pushrods may be subject to impact force variations of from zero to 1500 pounds at 5000 times per minute. In addition, the forces may be applied over a 20 to 30 degree arcuate variation in direction relative to the valve seat area.